Power control



oct. 7, 1947 c. F. scHoRN POWER CONTROL Filed May 17, 1943 8Sheets-Sheet 1 aorn INVENTOR Oct. 7, 1947. c, F. scHoRN 2,428,531

POWER CONTROL Filed May 17, 1943 e Sheets-sheet 2 NN m,

ATTORNEY C. F. SCHORN Oct.. 7, 1947.

POWER CONTRQL Filed May 17, 1943 8 Sheets-Sheet 3 INVENI'OR.

TMR/vir C. F. SCHORN POWER CONTROL Oct. 7, 1947.

8 Sheets-Sheet 4 Filed May 17, 1945 W m A m 0%; i v y RM i H J hm QM QNNINVENTOR.

n N m A oet. 7, y1947. C, F SCHORN' 2,428,531

POWER CONTROL C. F. SCHORN POWER CONTROL Filed May 17, 1943 8Sheets-Sheet 6 -Lqrz i? JMW INVENTOR.

ATTRNEY Oct. 7, 1947. c. F. scHoRN POWER CONTROL Filed may 17, Lema,k

8 Sheets-Sheet 7 INVENTOR.

A 7'7' ORNE Y Oct. 7, 194:7l c. F. Scl-:ORN

` POWER CONTROL Filed May 17, 1943 8 Sheets-Sheet 8 NUI/d n v NNN NQ RONINVENTOR.

ATTORNEY Patented Oct. 7, 1947 OFFICE POWER CONTROL Carl F. Schorn,Detroit, Mich., assignpr to George M. Holley and Earl Holley*Application May 17, 1943. lSerial No. 487,329

The object of this invention isto simplify the controls of an airplaneengine induction system. Generally, it is necessary to control therelationship between engine speed and manifold air pressure.Specifically, it is`desirable to relieve the pilot from the exercise ofany discretion so that he can concentrate on the business at hand. Atthe same time, provision must be made so that he can in an emergency,especially in a military emergency, exceed the safe limit of horse powerand of torque. Another object of this invention is to automaticallypermit the manual operation of these various devices when the automaticdevices are put out of action.

Fig. 1 shows the general arrangement of the preferred form of myinvention.

Fig. 2 shows the control devices illustrated in Fig. 1, in greaterdetail.

Fig. 3 shows a cross sectional plan view of the plane 3--3 of Fig, 2.

Fig. 4 shows one of the principal details of Fig. 2 in the position forobtaining maximum power.

Fig. 5 shows a partial sectional plan view taken on the plane 5-5 ofFig. 1. I

Fig. 6 shows diagrammatically the relationship,

ze claims. (c1. 17o-135.6)

' servomotor valve within the servomotor piston I3. This piston I3.

between manifold air pressure and engine speed.

Fig. 7 shows the relationship between the altitude and power deliveredto the `propeller when the engine is automatically controlled by thedevice illustrated in Figs. 1-5.

Fig. 8 shows the application of my invention to an engine having a turbodriven supercharger.

Fig. 9 shows an enlarged detail in the control shown in Fig. 8.

Figs. 10 and 11 show two positions of the valve shown on the right handside of Fig. 2.

In Fig. l0, the valve is shown in the position in which the superchargerdriven gear is locked in low.

In Fig. 11, the valve is shown in the position which reverses the normaloperation ofthe supercharger gear shift mechanism.

Fig. 12' shows an alternative construction in which control deviceillustrated in Figs. 1 and 2 is modiiied in certain respects.

Fig. 13 shows the manifold air pressure control cams shown in the modiedFig. 12 looking .I at the plane I3I 3 of Fig. l2.

Fig. 14 shows the detail of the cam shown in Fig. 13 to a larger scale.-

In Fig. 1, I0 shows the -cockpit manual control lever II) connected to alink I I and so with a I2 concentrically 'arranged has two fdiametersand operates in the cylinders located `in the stationary body 84.

Concentrically located within the larger of the two diameters is apiston I8 spring loaded to the left by compression spring 98. Thispiston I3 is connected tothe throttle lever Il which controls thethrottle valve I5, which throttle controls the admission of air to anengine driven supercharger 38 which supplies air under pressure to theengine.

When the servomotor valve I2, Fig, 3 moved tothe right of the neutralposition shown, high pressure oilis admitted from passage 4I and flowsthrough the passage of piston I3 through the passage 86 and port 81 inthe valve I2 through the port' 88 in the piston I3 through the passageI9 in the piston I3 into the annular chamber 30 which is formed byreason of the fact that piston I3 has two diameters. This high pressureoil pushes piston I3 to the right and opens the throttle Ii.

Low pressure oil meanwhile escapes from the chamber 9| through thepassage 92 and port 33 in pistn I3 port 94 and passage 95 in the valveI2 passage 96 in piston I3, passage 81 in the housing 84 and so to thelow pressure oil outlet II). The piston I3 continues to move until ports88 and 93 are closed. It follows that for each movement of valve I2there is substantially an equal movement of piston I3.

A rack is provided in the right hand side of large diameter piston I3(Fig. 2). This rack engages the pinion I8 so that an upward movement ofpiston I3 to open the throttle, causes the Dinion I8 and the 1ever'22mounted therewith to rotate clockwise.

The lever 22 is connected through a pin Joint 32 to a broken link 23which is connected through a pin joint 6I to a lever 2| mounted on theshaft 28. The movement of the cockpit lever I0 clockwise, thereforecauses the throttle to be initially opened less than the degree ofopening that will finally be required and at the same time rotates theshaft 28 clockwise to select the speed desired. Keyed to the shaft 20 isthe engine speed control pulley 24, Fig. 1. A clockwise rotation o fpulley y 24 causes thepulley 25 to rotate clockwise by means of thetransmission beltll which connects the two pulleys together'. Thisrotation of the pulley 2'5 adjusts the spring load on thregoverrior` 60which controls the speed of the variable`pit'ch propeller'l35 by meansof the serv'iotor valve |36, which controls the servomotm-J] by Lmeansofthe hydraulic transmission pipe I38`.`The den tails ofv the servomotor|31 which controls the "fective below approximately 1,200 R. P.. M. and

since the engine speed below 1,200 R. P..M. is a.V function of throttleposition onlyritls `necessaryV to provide the lost motion link 23,Fig.-`2.-\'-I'his link permits the movement of the throttle I; bythe'actionof piston I3 from the closed-'throttle position to thatcorresponding to 1,200 R. P. M.,

the position shown, before the speed control shaft begins to rotate; Ashaft 21, Fig. 2'is alsodriven by a exible tachometer drive connecteditoanY engine accessory drive at engine speedor at a fraction of enginespeed. A governor 28 is driven by`shaft 21 and controls ,the position ofservomotor valve 2 9 whichv is located Vconcentrically within andcontrols a servomotor piston 30 which rotates the shaft 32 through thelever- I2 I which isconnected by a, link 3| lto the servomotor pis- Highpressure oil for-operating the servomotor 30 is admitted. through thepassage 4| and low pressure oil escapes through the passage 40. "Therotation of theshaft 32 causes cam 33 to vengage with the spring loadedcam follower 34 which compresses the evacuated' capsules 35'which arelocated in chamber 36 which chamber communi-I cates Vwith pipe 31 withthe supercharger38 (Fig.

1). ConnectedY to the capsules 35 is .the servo.-

motor valve 39" (Iig.` 2), which controls the movement of piston |6inthe cylinder within the larger diameterof the two diameter piston I3.

The initial opening of the throttle I5 yin response to the movement ofthe piston I3 described above,

is insufficient to give the desired'relationshipbetween the engine speedand the manifold air pressure. The capsules 35 are thus expanded .from

thelength shownand the servomotor valve 39 is moved down from the.neutral position shown. High pressure oil from passage 4I is lplaced incommunication through an annular port in servomotor` valve 39 with theunderside of the piston I6 throughthe passage 42 causing it to rise. Lowpressure oil ispermitted to escape from the upper side of piston I6through passage 43 and through the upper annular port of valve 39 to thelow pressure oil passage 40, The piston I6 continues to open thethrottle I5 until the manifold air pressure and therefore the pressurein chamber 36 reach the desired value at which time the increase inpressure has caused the capsules 35 to decrease in length to return theservomotor valve 39 intothe neutral position shown. It is apparent thatthemanifold air pressure at which the servo valve 39 is moved into itsneutral position is a function of the positioning of top of the capsuleassembly 35. VIl the capsule assemblies are further depressed by theaction of cam 33, it will require a higher pressure in chamber 36 tocollapse the capsule assembly still further to return the valve to itsneutral position. Since the V4cam 33 isfrotated into a definitepositional; each \plotted against the speed. Wtilethe reached and thethrottle I5 has been opened by Y mentk of pin44, Fig. 4, compresses thespring 45 Y and the lever 46 is'thus moved clockwise and the,

engine speed, it followsfthat thecontour o! cam *I `93will determine therelationship that ,will exist between manifold air pressure and enginespeed. r As the throttle lever I0 is moved clockwise to .rotate thespeedC Qntrol shaft 20 to a Vposition Y corresponding to maximum' engine speY theesY manifold air pressurefollows the curve Y ofv Figf `in which themanif d air pressure is I polntQ is the action of pistons I3 and I6 to aposition rresponding.. to normal maximum superchargei"\v n gages with apin 44m-It will be noted that'in the L position shown in Fig. 4, fartherrotation of the pinion I 8 causes the lever 2 Ito rotateon-ly anegligible amount. A lever 46, Fig. 2,\is pivoted at#` sule 35 maintainthe lever 46 in equilibrium. V"The lower spring Y41 is accessiblefor'convenient adjustment andmodication. A downwardmovevalve 39 is thusmoved downwardly out' of the neutral position'in which it is shown sothat'high` pressure oil is admitted through the passage-4I,

isadmitted to the'underside of piston Iii-and throttle I5 isopenedfurther to raise supercharger pressure along the lineQRS, Fig. 6.i

1Ihe resulting )increase inl superchargur pressure is obtained with onlya negligible increase in the revolution Vper minute of theengine. Inother words, the line QRS isfsibstantially/vertical.4

Fig. 5 showsVA afnanual means' wherebyithe supercharger pressure-can beincreased beyondA the pressures determined by the action of cam 33 sothat a pressure of:29.2" Hg can be obtained at 1,400 R. P. M. instead of19" Hgautomatically called for by the contour of cam 33. For moreeconomical engine operation, it is desirable to opl erate the engine atthis pressureV of 29.2" vHgy at,

1,400 R. PfIM., andwtormaintainthis 29.2 oi

superchargernpressure ,constant up to .2,100

mais mounted on the shaft a2 around the' @am 33. The cam l|40 is rotatedbyY means of the push and pull shaft I4I which is connected to the leverV|42 which rotates the cam |40' by means of the pin |43.` When thiscamjis rotated, it depresses Y the cam follower 34,- Fig. 2,r therebylowering "the top of the capsule assembly 35 and causesvalve` 49 todescend andas is describedabove, causes the throttle I5 to open untilthe pressure in chamber 36 reaches 29.2"'Hg. In Athe normal course ofoperation, the shaft 32 is rotated in response to increasing enginespeed and the cam 33 Aremains ineffective` until the engine Vspeed hasreached.2,100lR.` P. M. at which time thelift of cam 33 equals that ofcam |40. This corresponds to point N on the curve LMN in Fig. 6.Atengine speeds in excess of 2,100 R. P. M., the cam 33 once more takesover thef positioning of thetop' of capsule 35. y

When starting thev engine before enginefoil underv pressure is availablelandwhen the throtties are closed'and consequently the piston I3islocated to the left of the position shown, piston |05-, Fig. 3, is heldto-therightof the position position MONoffFig.' 6, corresponds amasarv|04 is' held to' the' left of thepositions'hownrby the compressionspring |06. .These pistonstake up-the lost motionbetweenservo valve I2.and

engine operating conditionais needed topermit the servo valve I2 tofunction. It is to benoted that with the lost motion between valve I2and piston I3 eliminated and with piston I6 heldto the y left by thecompression'spring 98, a direct mechan 310 ical link exists betweencockpit lever I and `throt\ tle I5. 'To permit the free movement ofpiston I3 in response to the forceapplied on the'cockpit'lever I0, it isnecessary to provide free communication between the chambers 90`and' 9|on each side of ,15

the larger diameter of the two diameter'piston I3. It' is also necessaryto make/. provisionsfor the vdisplacement of the greater volumeo'f oilbeingdisplaced fromthe right chamber `9I'than the volume of oil thatwillbe takenv into the left 20 chamber 90 when the piston I3 is\' movedftothe right.` Thisl is accomplished by the action of piston valve IIIwhichr is located 'so as to' in-v f terrupt the passage.|14-I15. Whenstarting 'the engine before oil under vpressure-is available,`pis 25vton valve III is pushed to thyeftfof' thegposition shown by the actionofvcompression spring II2. With the valve' in the left position,f.chambers 90 and .9| are inv free communication with each other` through.thep'assages I14,g I`I3, and -v 30' |15. 'Ihe excessive oilzin chamber'9| vescapes through passage |14' invalve III and through. the

low pressure oilpassage40. y

With thepiston. in itsy full left position, the oil passages 42 and -43are\in vcommunication with'135- each other through? the passage II8,short circuiting passage 99, .and passage I00,.'therefore (Fig.v 2), theservo valve 39'which controls manifold air pressure, the controlmechanism'v is ineffective to move piston I6. Itl follows that the .40

throttle I Astarting from idle i yengine speed and continuing up to.1,200 R. P.V M. (at -which position the piston I3 has'moved into/theposition shown toA close the shc-rtcircuiting passage 99) is positivelycontrolled bythe manually-opeV 45 erated lever I0. When theengine isstartedand oil pressure is obtained, cil under pressure flows throughpassage 85 into the vchambers |08 and I02'forcing the piston I05 to theleft" and I 04to the right thereby. centering the servok valve I2. "'5'0The oil to the left of |05and to the right of." |04 escapes tothelowpressure outlet. At `the same` time, oil under pressure is admittedinto the chamber IIS through 'passage I I5 pushing the valve III totheirighttointerrupt the passages :55

| and |14. In the case of an oilfailure, the system automaticallyvreverts to the manualtcontrol system described above.

Oil escape .passage ||9 (which connects theV chamber I I1 to theleft ofvpiston I6 ywith the low 60 pressure oil passage 40. through passages-91and IIS, I'I8, and I0| when piston. I3 is moved' left from the position`shown-in Fig. 3 to open this bypass II 9) isprovided to permit a' quickreturn of piston I6 vto its full' left position whenit is 65',

desired to quickly return. the engine operation to idle output bypulling' the manual control lever I0 back into its idle position.

Let us assume `that the` plane climbs under the fmanifoldairpressureandthe brake power fall alongthe lineLBC. The throttle remains open thepiston I3'- whichlostsmotion underV normal 5 4..untilwat the point C,the v`manifoldvr air'pressure liasffallen.toapproximately 24" mercury.The

creased supercharger.v pressure acting on the 1 chamber 36 and\then.cause'd to open to maintain the manifold air pressure constant at29.2" mercuryduringthe period the plane is climbing from16,000/\to`18,00'0 feet-that is, from the point C ytopo'intDl in` Fig.6. Atzpoint D the throttle is again wide open. Thereafter the powerfalls along the line DE duringwhich time the throttle r"is Iwide open.The point C is selected so that loss-of power in driving thesupercharger at its 'higherspeed balances theigain in power by restoringthe manifold air pressure to 29.2" mercury. 'Iti is vto benoted thatVwhen operating along lines BC .and DE; the throttle I5 is held againstits"\wide open stop. Under these circum r f stances, unless specialmeans are provided,- oil -under 'pressure in chamber II1 would backlload the piston I3 andV thereby ca use objectionable ,back loading onthe manual lever I0 located in: the cockpit. Since the cross sectionalarea.' of chamberil4 is madeequal to or. larger than the cross sectionalareav of piston I6 and since acommon high pressure oil source is used inboth char'nbers,` there is always suilicientV force acting onvthedifferentialjarea of the two diameter piston I3 to overcome the backloading force created by the oil'under pressure in cham- .ber\| I1.Hence, the problem of back loading vis eliminated by'zthe inherentcharacteristics of the'deslgn. f

y Automatz'cgearfshift .l Thesupercliarger gear shiftat pointvC,'Fig."1,

is obtained by the following mechanism, right hand sideoi" Fig. 2. A cam52 iskeyed'to shaft 32 andengages with a. yspring loadecl`follower53`whichi engages with evacuated capsules49'1ocatedv .ina chamber 50 whichis maintained at atmospherlczpressure through a, passage`5I. This` cap-Vsuie 49is` connectedv to a servomotor valve 48 .which controlsaservomotor piston 54 which conpands due.todecreasedatmospheric pressurein I chamber 50ys'uiciently to rotate a bell crank lever 55V mounted on`a .pivot64 so as toforcea rol1er'65 pasta springloaded button56. Thislower valve' 48' is-'then'past the-neutral positionr shown so thathigh'pressure oilris admitted from the passage A 4| rthrough a port" invalve 48 to the underside of the piston 54 throughthe'passages v|22 and|24.

1Lowpressure oil above the piston 54 escapes through IthepassagesI261and |28 through the upper-annular portv in valve 48 tothe lowpressure oil passage' 40. The piston 54V rises through its full travelcarrying Awith it'its link 61. This link lI1 rotates a bell crank lever68, Fig. 1, clockconditions corresponding'to point NFig.' I5, that`70wise, whichraises a link 10 and rotates the lever gneand the planeclimbs along ABjFig. 7. At 75' 69 anticlockwise causing a clutch 1I toengage Ywith a clutch 14 which causes the clutch 14 to rotate fasterthrough an over ride` clutch (not vshown)vmounted inside 14 on4 shaft13,1which is the lowspeed driven shaft. The .highspeed shaft.

' the lower speed.,

amasar 7 12 thus drives the clutch 1| and clutch 14 which drives thebelt 415 and causes the superchargerl 38 to rotate at higher speed. Asthe plane' cle--` scends, when the point C, Fig. 7, is reached, the

supercharger does not revert to low speed immef l diately but remains inhigh speed until the point F is reached, 15,000 feet. At this point, theinfluence of the increasing atmospheric pressure on the capsule assembly49 and therefore on the` valve 48 has become sufficient to rotate thepressure bell crank lever 55 counter-clockwise, first compressing thespring loaded buttonv 56 and then releasing it. Ilhe valve 48 ascendsabove the neutral position shown in Fig. 2.` This places` mechanismmomentarily after each 2l/2 hours of engine operation to clear out theoil passages f the clutch system. It is considered advisable alsoA to berable `to operate at all altitudes in low supercharger speed ratio. Toaccomplish this, valve v |20, Fig.V 2Fig. 10, Fig. 11, which-is manuallycontrollable through'the linkage |80, IBI, |82, |83 and shaft |84' whichis attached to valve |20 is interposed in the oli lines from the servovalve 48 tothe cylinder Vcontaining piston 54V. When the valve isrotated 45 degrees clockwise, into the position shown inFig.y 11 fromits neutral position inA which it is shown in Fig. 2, passage |28communicates With'passage |24 and passage |22 drive to its low speedposition, that is to say,

the clutch 1l is disengaged from the clutch 14 and the low speed shaft13 takes up the load and drives the belt 15 and the supercharger 38 atThe Vpower immediately increases along line FG, thereafter, the throttleremainsr Wide open along the line GB. At the point B, the superchargerpressure has reached the desired 29.2" of mercury and the throttle isclosed bythe mechanism already. described to maintain` 29.2" manifoldair pressure and the horse power decreases along the line BA, the speedof engine being constant at all times at 2,100 R. P. M. For bestperformance, the altitude at which the shift' in supercharger speed ismade varies with engine, speed. Since the cam 52 is rotated as afunction of engine speed and since the lift of cam52 positions top ofcapsule assembly 49, it

is quite obvious that by properly contouring the v cam 52 anydesiredrelation between engine speed and supercharger shift, and altitude maybe obl tained.

l' It is desirable at above rated-engine speed to prevent the clutch1|-14 from being engaged or disengaged and the drive of the superchargerbeing lock pin 58 normally an integral part of cam.

follower 11.. The cam follower 11 is forced to engage with cam 16 by thecompression spring 18 `which is seated in the element 83 and presses.upward on lcck pin 58. When the engine speed is increased above 2,400R. P. M. pinv 58 is depressed by the cam 16 and engages with springloaded button 56 pushing it down against the shoulder on element 82 andtherebylocking the bell crank lever 55 in either of its two operativepositions, that is to say, either the with servomotor valve 48 in itsabove neutral position or in its below neutral position. Element 83 alsoprovides a seat for the compression spring 51 and serves as a means toadjust the compression load 0f spring 51. Safety spring 19/ is providedto protect the mechanism from being jammed if the shaft 32 wererotatedywith the lever 55 in the position shown.

It has been found advisable under normal engine operation/'to shiftthesupercharger clutch is in cornmunication with passage I 26. Byy thismeans, the supercharger speed is shifted from `its operating speed toeither high speed'or low speed depending on speed at which it is at thetime the shift is made.

When the valve |20 is rotated 45 degrees counter-clockwise into theposition shown in Fig. 10,

operating passages |26, |24, |28, and |22 are all infcommunication witheach other through the passage |21 located in the stationary centersection of the valve assembly. `With all of the oil passages incommunication with each other, the piston 54 is forceddown and held bythe compression spring 66 into the lowered position shown in Fig. 2which position corresponds to the low speed ratio operation of thesupercharger.

Exhaust driven supercharger In Fig s, Isn Vindicates the engine, `l'slindicates the exhaustpassage delivering the exhaust to the impeller y|10 of the turbo-supercharger |52.

This supercharger is controlled by `an exhaust of Fig. 2 omitting themeans for shifting the change speed drive means of the two speedsupercharger` This supercharger control mechanism shown on the right ofcontrol device in Fig. 2 is replaced by the control unit |65 which iscontrolled by the pressure of air entering the carburetor. This pressureis made effective through the pipe |66. The carburetor outletcommunicates with air entrance leading to the engine driven supercharger|68 which delivers the compressed mixture to the manifold |69 whichsupplies mixture to the engine |50. As in Fig. 1, a pipe 31 connects thethrottle control unit |64 with the manifold I 69.

In Fig. 9, the pipe |66 is shown connected with the chamber |10 in whichthere yislocatedan evacuated bellows 256 which mayV be ladjustablylocated by means of the eccentric element 304. The evacuated capsuleengages with the servomotor valve 300. This servomotor valve 300controls the piston 301 by means of the passages 266 and 258. Thelocation of the top of the capsule assembly 256 is adjusted by means ofeccentric 304 so that when the pressure in the carburetor inlet exceedsthat corresponding to 7,000 feet, the length of the capsule assembly 256is such that the servo valve 300 is left of the neutral position shown.At altitudes below 7,000 feet, high pressure oil communicatesthrough-the passage 4| owsthrough the annular passage in the servomotorvalve 300 through the passage 266 ,Y

capsule assembly 256 expands sufficiently to move the servomotor valve300 to the right of the neutral position shown and high pressure oilflows from 4| through the annular passage in the servomotor valve 300through' the passage 250 and pushes the piston 301 to the leftcompressing a Meanwhile, low pressure oil from the spring |1 I.

throttle valve I5 is entirely dependent upon the manual operation oflcockpit lever I0.

left of piston 301 escapes through passage 266.,

through the annular passage in servomotor valve 300 out the low pressureoil passage 40. `Piston 301 continues to move to the left, therebyclosing valve |53 forcing more of the exhaust gases to pass throughmotor ofthe turbosupercharger.

The speed of the supercharger is increased causing an increase in airpressure in the carburetor inlet. The piston` 301 continues to move tothe left until the pressure inthe carburetor inlet equals thatcorresponding to k'1,000 feet altitude at which time the pressure in thechamber causes the capsule length to return to that length necessary toreturn the servomotor valve to the neutral position shown.

The performance of an engine equipped with the supercharger. and controlsystems shown in Fig. 8 and Fig. 9 would be as follows: rI he planewould ascend along the constant speed and constant manifold air pressureline AB, Fig. 7, untily point H is reached and then continues to ascendalong the substantially constant power line HJ. At J, the exhaust valve|53 has been pushed to itsI closedmposition, the throttle |59 has becomeopened toits wide open position.y A continued climb causes power to falloff along JK.

The reason the power remains substantially constant from point H to J isthat the back suction on the enginev exhaust system above r1,000altitude is maintained substantially constant by the operation of theexhaust valve |53.

Above 14,000 feet there is a marked advantage in horse power with theturbo-supercharger over the gear driven supercharger.

the supercharger cancel some of the gains especially at extreme speeds.Hence, the gain is more pronouncedwith a bomber than with a fighter.

The use of two governors is `justified by the However, the loss', in jetpropulsion when the exhaust is used to drive extension of lever 22engages with pin 20| and thus raises the vertical shaft 200. A shoulder202 on the`shaft 200 then engages with a lever 204 and rotates it arounda pin 205 which corresponds to the pin |22 of Fig. 2. Lever 204corresponds to the lever 46 of Fig. 2. When this happens, the servomotorvalve 39 is lifted above its neutral poistion in which it; is shown. Aspring loaded locking pin 203 locks the shaft 200 in thiselevatedposition. With the valve 39 thus elevated, high pressure oil isadmitted above the piston I6 forcing it\ into a downward position (Fig.2) in which the position and control of the In Figs. 12, 13, and 14 theshaft 206' corresponds to cam shaft 32, Fig. 2. This shaft 206 is keyedto `idle cam 20'|,-Fig. 14, which cam compares with the cam 33 of Fig.2. An"` additional cam 208 is rotatalzvly mounted yon shaft 206.'v Therange of rotation of cam 208 is limited in the clockwise di- ;y recaenbyan adjustable stop :lo and its movefact that the second governoris'built into the r power control and serves to make the operation ofthe control independent of the inconsistences due to hysteresis andtolerance found in the governor built into, the propeller assembly.

The use of th'e second governor makes my unit self contained, capable of,being calibrated on a tesi; bench, independent of the propeller unit orplane installation.

Fig, 12 shows a means for locking the evacuated capsule assembly 35 outof action in theevent that this capsule is ruptured and it will tend ntoexpand. In Fig. 12, the lever'22 is, provided with" a fork whichextended to the right and which engages with a pin 20| guided in a slotin the hollow stem 44. Pin 20| engages with a rod 200 which slidesinside the hollow stem 44. The Vrod 200 then compresses a spring whichnormally.y

ment is limited in the opposite direction, anticlockwise, by a movablestop 209. This movable f stop 209 is moved by theoil under pressureadmitted through the passage 2||\ which passage is located in shaft 206and which passage communicates with cylindrical chamber below piston 54,Fig. \12. The other oil passage 2|2 communicates with the low pressureoil system 40 and with the right hand side of th'e piston operating thestop 209.` The operation of mechanism just described is as follows:

4 When the engine is put in low supercharger gear and consequentlypiston 54 is in position shown in drawing the cam 201 selects themanifold air pressure for each speed as before. When high pressure oilis admitted belowthe piston 54 to change gear ratio to high superchargergear ratio, then high oil pressure is admitted to move the stop 209 tothe right, compressing the spring 2|3 and substituting the cam 200 forcarriv 201, which thus gives an alternative relationship between 4speedand manifold air pressure in high blower.

In Fig. 13, the manually operated cam 2|4` corresponds to cam |40, ofFig. 2. When the lever 2|5 is manually moved in the anticlockwisedirection, cam 2|4 rotates clockwise the lever 2|6 through theadjustable stop 2|'| which lowers the cam follower 34 so as to obtainthe cruising override performance vcurve ON shownin Fig. 6.

What I claim is:

1. In` combination with an internal combustion engine having an enginedriven supercharger adapted to deliver air to said engine, an airentrance to said supercharger and a throttle valve, control linkagetherefor adapted to control the air flow through the air inlet, a.`(variable pitch propeller driven by `aid engine having `a spring loadedcentrifugal governor adapted to control the engine speed by varying thepitch of said propeller, a control linkage for said governor adapted toselect the speed of the engineby varying the load of the governorspring, a manually operated control lever, a motion transmissionsysvtern connecting said control lever to said throttle valve controllinkage and also connecting said lever to said control device for saidpropeller governor control, a second engine driven centrifugal governor,a barometric responsive device, a variable pressure chamber enclosingsaid barometric device,`fa pipe connecting said chamber to the airtrifugal device and by said barometric means, a

servomotor controlled by said valve saicl motor being interposed in saidmotion transmission system whereby after the throttle has been manuallyopened a relatively small amount, it is opened automatically anadditional amount by said servomotor so vas to maintain inthe outletfrom said supercharger a preselected pressure, corresponding to theselected engine speed.

2. A device as set forth in claim 1 in which there is a superchargerdrive having two speed ratios at either oi which the supercharger may bedriven, means for automatically selecting the speed comprising a secondbarometric means `re1- sponsive to the atmospheric pressure, a secondservomotor valveA adapted to be controlled byf both said secondcentrifugal governor and by said second barometric device, means forselecting the speed ratio of said supercharger comprising a secondservomotor responsive to and controlled by said second servomotor valveadapted to select the speed of the supercharger at a preselectedaltitude corresponding to each selected engine speed so as to maintainthe pressure entering f the engine at the desirable value correspondingto the selected engine speed. y l

3. Device as set forth in claim l /ln which the said motion transmissionsystem connection cornprises a two diameter piston adapted to slide in atwo diameter stationary cylinder and in which a `second` servomotorvalve is located within the smaller diameter of said two diameterpisvariable pressure chamber\enclosing said baro-l metric device.

5. Device as set forth in claim 1 in which the saidmotion transmissionsystem connection comprises a two diameter piston adapted to slide in atwo diameter stationary cylinder andin which a servomotor valve islocated within the smaller diameter' of said two' diameter piston andadapted to move the said two diameter piston in the direction of themovement of said servomotor valve by an' amount substantially equal tothe movement of said servomotor i alve by admitting high pressure oileither into ytldinular chamber created by the difference in meter of thesaid two diameter piston or into the chamber formed by the opposite faceof larger diameter` of the two diameter piston and the cylinder walls,low pressure oil meanwhile being permitted to escape\from the chamber towhich the high pressure oil is not admittedand in which there is aspring loaded smaller piston within the larger diameter of saidy twodiameter piston controlled by said second centrifugal device and by saidbarometric means said smaller piston being directly connected to saidthrottle linkage and in which the area of the smaller piston is.substantially equal to the diiference in the area ton and adapted tomove the said two diameter piston in the direction of the movement ofsaid servomotor valve by an amount substantially equal to the movementof said servomotor valve by admitting high pressure oil either into theannular chamber created by the diierence in diameter of the two diameterpiston or into the chamber formed by theopposite face of larger'diameter of the two diameter piston and the cylinder walls, lowpressure oil meanwhile being permitted to escape from the chamber towhich the high pressure oil is not admitted and in which there is aspring loaded smaller piston within 'the larger diameter of said twodiameter piston controlled by said second centrifugal de-` vice and bysaid barometric means said smaller piston being directly connected tosaid throttle linkage and in which the area of the smaller piston issubstantially equal to the difference in` the area between the area ofthe larger diameterV and the smaller diameter of the two diameter pistonso that the back load on the large -piston due to the high oil` pressurebehind the smaller piston when the throttle is opened wide is sub-`stantially balancedr by the high il pressure acti ing in the annularchamber to push the two diameter piston forward.

4. Device a`s set forth in claim 1 in which the mechanism connecting thepropellerY controlling device with the throttle control lever is sodesigned that when the propeller controlling device approaches theposition corresponding to the desired maximum speed of the engine, the

influence of the further movement of the throttle control mechanism onthe speed of the engine controlled supercharger pressure to increase thei becomes negligible although its influence on the means of springloading the said servomotor l valve thereby producing the same. resulton the balance of the supercharger lpressure control system as aninsufficient pressure within the said between the area of the largerdiameter and the smaller diameter of the two diameter piston so that theback load on the large piston due to the high oil pressure behind thesmaller piston when the throttle is opened against its wide open stop issubstantially balanced by the high oil pressure acting in the annularchamber to push the two diameter piston forward andin which there existswithin the motion transmission system spring loaded pistons adaptedautomatically to take up the lost motion that would otherwise existbetween the ends of the servomotor valve contained in the Vcylinderlocated within the smaller diameter of the two diameter piston and theend walls of the said cylinder when starting the engine before high oilpressure exists ed to move the said two diameter piston in the vdirection of the movement of said servomotor valve by an amountsubstantially equal to the movement of said servomotor valve byadmitting high pressure oil either into the annular cham. ber created bythe diilerence in diameter of the Y two diameter piston or intol thechamber formed by the opposite face of larger diameter of the twodiameter piston and the cylinder walls, low pressure oil meanwhile beingpermitted toescape from the chamber to which the high-presi sure oil isnot admitted and in which there is a spring loaded' smaller pistonwithin the larger diameterof said two diameter piston controlled l bysaid second centrifugal device and by said barometric means, saidsmaller piston being directly connected to' said throttle linkage andin* which the area of the smaller piston is substanc tially equal to thedierence in the area between the area Aof the larger diameter and thesmaller di` ameter of the two diameter pistpn so that the back load onthe large piston due to the high oil prespistons adapted automaticallyto take up the lost motion that would otherwise exist between `the endsof the servomotor valve contained in the cylinder located within thesmaller diameter of the two ,diameter piston and the end walls of thesaid cylinder when starting the engine before. high oil pressure existssaid spring loaded pistons being adapted to automatically release thesaid servomotor valve when the .oil pressure increases in response tothe rotation of the engine and in which there exists an oil vescapepassage connecting the chambers formed by the stationary cylinder andthe end faces of thev larger diameter of the two diameter piston\and anautomatic shut off valve within the said oil escape passage so adaptedthat when starting the engine before high oil pressure exists a fr ecommunication exists between the said chambers and the low oil pressureside oi.' the system enabling the free movement of said two diameterpiston and so adapted that as the engine begins to function theautomatic valve stops the escape passage joining the said two chambersand stops the escape passage from the low oil pressure side of thesystem.

7. Device as set forth in claim 1 in which there is ,a superchargerdrive having two speed ratios at either of which the supercharger may bedriven, means for automatically selecting the speed comprising a secondbarometric means responsive to the atmospheric pressure, a servomotorvalve adapted to be controlled by both said second centrifugal governorand by said second barometric device, means for selecting the speed ofsaid supercharger. comprising a servomotor responsive to and controlledby said second servomotor valve adapted to select the speed of thesupercharger at a preselected altitude corresponding to each selectedengine speed so as to maintain the pressure entering the engine at thedesirable value corresponding to the selected engine speed and in whichthere exists a valve interposed in the oil lines from the servomotorvalve and the spring loaded servomotor piston adapted when moved tochange the supercharger speed so that the supercharger speed ratio canbe manually changed at any time by the movement of said interposed valvefrom its neutral position and also by an additional or opposite movementof the valve from its neutral position the supercharger can bemaintained in low speed ratio independently of engine speed or altitude.

8. Device as set forth in claim 1 in which there isqa supercharger drivehaving two speed ratios at either of which the supercharger may bedriven, means for automatically selecting the speed comprising a secondbarometric means responsive to` the atmospheric pressure, a servomotorvalve adapted to be controlled by both said second centrifugal governorand by said second barometric device, means selecting the speed of saidsupercharger comprising a servomotorv responsive `to and controlled bysaid second servomotor valve adapted to select the speed of thesupercharger at a preselected altitude corresponding to each selectedengine speed so as to maintain the pressure entering the engine at thedesirable value corresponding to the selected engine speed and in'throttle \pressing and then releasing said snap button so that theaction of the said servomotor valve will cause the said servomotorpiston to travel unhesitatingly either to low or high supercharger speedratio position. l.

9. A device as set forth in claim 1 in which there is a superchargerdrive having two speed ratios at either of which the supercharger may be driven, means for automatically selecting the speed comprising asecond barometric means responsive to the atmospheric pressure, aservomotor valve adapted to be controlled by both said secondi.centrifugal governor and by said second barometric device, means forselecting the speed .A

` speed and in which there exists trip over mechanism comprising a leverand a spring loaded snap button and a means to adjust the spring load onthe said snap button, a lever attached to the said servomotor valve andadapted to cause the said valve to snap through its neutral position byiirst depressing and then releasing said snap buttonso that the actionof the said servomotor valve will cause the said servomotor piston totravel unhesitatingly either to low or high supercharger speed ratioposition and in which there exists a spring loaded compressible shaftwhich is controlled by means of a cam which is positioned by the actionof said second centrifugal governor and which shaft isl adapted tocontact said spring loaded snap button at a predetermined speed and allengine speeds in excess of said predetermined speed to force in downwardso that the said servo valve controlling the supercharger shiftservomotor piston is held on either side of its neutral position.

10. Device as set forth ,in claim 1 in which the said motiontransmission system connection comprises a two diameter piston adaptedto slide in a two diameter stationary cylinder and in which a servomotorvalve is located within the smaller diameter of said two diameter pistonand adapted to move the said two diameter piston in the direction of themovement of said servomotor valve by an amount substantially equal -tothe movement 'oi' said servomotor valve by admitting high presl oppositeface of larger diameter of the two diameter piston and the cylinderwalls, low pressure oil meanwhile being permitted to escape from thechamber to Which the high pressure oil is not admitted and in whichthere is a spring loaded smaller piston within the larger diameter ofsaid two diameter piston controlled by said second centrifugal deviceand by said barometric means said smaller piston being directlyconnected to said throttle linkage and in which the area of the smallerpiston is substantially equalto the difference in the area between thearea of the larger diameter andthe smaller diameter of the two diameterpiston so that the back load on the large piston due to the high oilpressure behind the smaller piston when the throttle is opened against`the wide open stop is substantially balancedby the high oil pressureacting in the annular chamber to push the two diameter piston forwardand in which the porting of the said two diameter i piston and saidstationary cylinder is such so that said servomotor interposed in saidstraight through motor transmission system is made inoperative when thesaid two diameter piston is moved to a position corresponding to lowengine speeds and low engine power output.

11. Device as set forth in claim 1 in which the said motion transmissionsystem connection comprises a two diameter piston adapted to slide in atwo diameter stationary cylinder and in which av servomotor valve islocated within the smaller diameter of said two diameter piston andadapted vto move'the said two diameter piston in the direction of themovement of said servomotor valve by an amount substantially equal tothe movement of said servomotor valve by admitting high manuallyoperated control lever and the said throttle valve control linkage andisarranged s0 as to give `a straight through transmission system.

14.y Device as set iorth in claim 1 in which the said motiontransmission system connection comprises a two diameter piston adaptedto slide in a two diameter stationary cylinder and in which a secondservomotor valve is located within the smaller diameter of said twodiameter piston and adapted to move the said two diameter piston in thedirection of the movement of said servomotor valve by an amount,substantially equal to the movement of said servomotor valve byadmitting high pressure oil either into the annular chamber created bythe difference in diameter of the two diameter piston or into thechamber formed by the .opposite face of larger diameter of the twoadmitted and in which there is aspring loaded smaller piston within thelarger diameter of said two diameter piston'controlled by said second`centrifugal device and by said barometric means said smaller pistonbeing directly connected to said throttle linkage and in which theareaof the smaller piston is substantially equal to the difference in thearea between the area of the larger diameter and the smaller diameter ofthe two diameter piston so that the back load on the large piston due tothe high oil pressure behind the smaller piston when the throttle isopened against the wide open stop is substantially balanced by the highoil pressure acting in the annular chamber to push the two diameterpiston forward andl in which there exists a manually operated camtocontrol the position of .said barometric element and thus over ride thecontrol of said second centrifugal governor sol that higher controlledmanifold air pressure can be obtained at any engine speed than wouldnormally be called for by the centrifugal governor control mechanism.

l2. Device as set forth in claim 1 in which the said motor transmissionsystem islocated between the said manually operated control lever andthe said Vthrottle valve control linkage and is arranged so as to give astraight through transmission system with the said servomotorconcentrically arranged within said system. u

13. Device as set forth in claim 1 in which there is a superchargerdrive having two speedV ratios at either of which the supercharger maybe driven, means for automatically selecting the speed comprising saidbarometric means responsive to the atmospheric pressure, a secondservomotor valve adapted to be controlled by both said sec- Aondcentrifugal governor and by said second barometric device, meansforselecting the speed ratio of said supercharger comprising a secondservomotor responsive to and controlled by said second servomotor valveadapted to select the speed of the supercharger at a preselectedaltitude corresponding to each selected engine speed so as to maintainthe pressure entering the engine at the desirable value corresponding tothe selected engine speed, and in which the said motor transmissionsystem is located between the said diameter piston and the cylinderwalls, low pressure meanwhile being permitted to escape from the chamberto which the high pressure oil is not admitted and in which there is aspringdoaded Smaller piston within the larger diameter of said twodiameter piston controlled by said second centrifugal device and by saidbarometric means said smaller piston being directly connected to saidthrottle linkage and in which the area of the smaller piston issubstantially equal to the difference in the area between the area ofthe larger diameter and the smaller diameter of the two diameter pistonso that the back load on the large piston due to the high oil pressurebehind the smaller piston when the throttle is opened Wide issubstantially balanced by the high oil pressure acting in the annularchamber to push the two diameter piston forward, and in which the said fmotor transmission system is located between the said manually operatedcontrol lever and the said throttle valve `control linkage and isarranged so i as to give a straight through transmission system with thesaid servomotor concentrically arranged within said system.

15. Device as set forth 'in claim 1 in which an engine exhaust drivensupercharger is adapted to delivering airA to said rst mentionedsupercharger and is connected in series therewith on 3the atmosphericside of said throttle valve, anv

exhaust throttle valve for controlling the ow l of exhaust' gases tosaid exhaust driven super.-

charger, means responsive to the pressure of the air owing from saidexhaust driven supercharger `for controlling said exhaust throttlewhereby when the pressure of the air ilowing from said exhaust drivensupercharger falls below a predetermined value the pressure is restoredsubstantially to that value until all the exhaust gases are beingutilized to drive the supercharger.

16. In combination with the device as set forth `in claim 1, in whichthe mechanism connecting the propeller controlling device with thethrottle control lever is` so designed that when the propellercontrolling device approaches the position corresponding to the desiredmaximum speed of the engine, the influence of the further movement ofthe throttle control mechanism on the .speed of the engine becomesnegligible although its influence on the controlled superchargerpressure to increase the manifold' air pressure of the engine continuesby spring loading the said servomotor valve thereby producing the sameresult on the balance of the supercharger pressure control system as aninsuilicient pressure within the variable pressure chamber enclosingsaid barometric -device and in which an exhaust driven supercharger isconnected on the atmospheric side of said throttle valve, an exhaustthrottling engine having an engine driven supercharger and.`

an air passage leading thereto having throttle valve located therein, anengine exhaust driven turbo supercharger connected to the air passage onthe atmospheric side of said throttle valve, exhaust throttling meansfor said second super charger adapted to control the operation of saidsupercharger, a variable pitch propeller driven by said enginehavingspring loaded engine driven centrifugal governor adapted tocontrol the engine speed by varying the pitch i said propeller? controllinkage for said governor adapted to select the speed of the engine byvarying the load on said governor, spring means for operating saidlinkage for selected said engine speed. said manually operated meansbeing also adapted to open the throttle to .a limited degree, a secondengine driven governor, a cam adapted to be controlled by said secondgovernor, a chamber in communication with the engine side of firstmentioned supercharger, evacuated capsules adjustably located in saidchamber by said cam, a servomotor valve adapted to be moved by thecombined effect ol the movement of said cam and the expansion of saidcapsules, servomotor means controlled by said servomotor valve andadapted to still further open said throttle valve until the superchargerpressure reaches the value determined by said cam for said specificspeed of the engine, ibarometric means responsive to the pressure in theair entrance of the atmospheric side of said throttle, said means beingconnected to said throttling means for said second supercharger andadapted to maintain the said air pressure at the pressure correspondingto a `\sele,cted altitude bykcontrolling the flow of exhaust gases tosaid exhaust driven turbo-super charger.

18. Device as set forth in claim 1'7 in which there are means forincreasing theJ rst mentioned supercharger pressure Without increasingthe speed of engine when the maximum desirable speed of engine isreached.

19. (Fig. 12). Device as set forth in claim 1 in which the mechanismconnecting the propeller control device with the throttle control leveris so designed that when the said manually operated throttle controllever is moved beyond the position of minimum throttle openingcorresponding to the minimum speed of engine said servomotor valve ismechanically locked into a position which prevents the said additionalopening of said throttle by said servomotor valve and thereby places thecontrol of said throttle exclusively under said manually operatedthrottle control lever.

20.' In combination with an internal combustion v engine having anengine driven supercharger adapted to deliver air to said engine, an airentrance to said supercharger and a throttle valve, control linkagetherefor adapted to control the air now through the air inlet, avariable pitch propeller driven by said engine having a spring loadedcentrifugal governor adapted to control the engine speed by varying thepitch of said 18 propeller, a control linkage lfor said governor adaptedto select the speed ofthe engine by varying the lload on the governorspring, a manually operated control lever, a `motion transmission systemconnecting said control lever to said throttle valve, control linkageand also connecting said lever to said control device for said propellergovernor control, a barometric responsive device, a variable pressurechamber enclosing said barometric device, a passage connec-ting saidchamber tothe air inlet on the engine side of said supercharger, a shaftadapted to control the manifold air pressure and to be rotated inresponse to variations in engine speed, a cam mounted thereon adapted toengage with said barometric device, a servomotor valve controlled bysaid cam and by said barometric device,l a servomotor controlled by saidvalve said motor being interposed in said motor transmission system, asecond cam mounted on said shaft normally adapted to be inoperative butadapted when rotated on said shaft to engage with said`barometric means,and in which there is a supercharger drive having two speeds, means forincreasing the speed of said supercharger and simultaneously moving saidsec-v ond cam so that it takes the place of said rst cam.

21. Device as set forth in claim 2O in which the means forincreasing.the speed of said supercharger comprises a'second lbarometricmeans responsive to the atmospheric pressure, a servomotor`valve adaptedto be controlledithereby and lby said `manifold air pressure controlshaft, a servomotor adapted to be controlled by said servomotor valve,hydraulic means interposedbetween said first and second cam andcontrolled by said servomotor and adapted to move said second cam.

relative t0Y said rst cam at the same time as saidy servomotor valveoperates said servomotor to change the gear ratio of said superchargerdrive so as to increase the speed of rotation of said supercharger.

22. In combination with an internal combustion engine for an airplane, asupercharger driven thereby and connected to deliver air to said engine,an air entrance to said supercharger, an air throttling valve therefor,an engine exhaust driven supercharger adapted to deliver air to saidenginedriven supercharger and connected in' series therewith on theatmospheric side of said valve, exhaust throttling meansor said exhaustdriven supencharger, automatic means responsive Ito the pressure createdby said engine driven supercharger for controlling said nrst mentionedthrottling valve, means responsive to the pressure created by saidexhaust turbine driven supercharger for controlling said exhaustthrottling means whereby, when the pressurein the exit from saidexhaust, turbine driven supercharger falls to below a predeterminedvalue, the said pressure is restored substantially to that value untilall the exhaust gases are being utilized to drive the superchargerf,

23'. In combination with an internal comlbustion engine for an airplane,a supercharger driven :thereby andy connected to deliver air to saidengine, 'an airI entrance to said supercharger, an air throttling valvetherefor, a carburetor associated therewith, an engine exhaust drivensupercharger adaptedto deliver air to said carburetor, exhaustthrottling means for said exhaust driven supercharger, automatic meansresponsive tofthe pressure created by said engine driven superchargerfor controlling said first mentioned throttling valve, means responsiveto the pressure crel 19 n ated by said exhaust turbine drivenvsupercharger for controlling said exhaust throttling means whereby, whenthe pressure in the exit from said exhaust turbine driven vsuperchargerfalls to below a predetermined value, the said vpressure is re- `5stored substantially to that value until all the exhaust gases are:being utilized to drive the supercharger.

, t CARL F. SCHORN.

REFERENCES CITED le of this patent:

UNITED STATES PA'I'EN'IS Number Name Date 2,297,235 Muller Sept. 29,1942 2,305,810 Muller Dec. 22, 1942 2,285,344 Marples et al. June 2,1942 2,355,759 Stokes Aug. 15, 1944 OTHER REFERENCES Ser. No. 304,834,Boulet (A. P. C.) pub. Apr. 27, 1943.

